Civil Engineering Reference
In-Depth Information
Table 4.2
Limits of amounts of deleterious substances for type H
recycled aggregates, JIS standard
Category
Deleterious substances
Limit (mass %)
A
Tile, brick, ceramics, asphalt
2.0
B
Glass
0.5
C
Plaster
0.1
D
Inorganic substances other than plaster
0.5
E
Plastics
0.5
F
Wood, paper, asphalt
0.1
Total
3.0
There are also upper limits set for the amount of deleterious substances
present in the type H recycled aggregate, as shown in Table 4.2. JSI A
5023 has also been published as a standard for recycled concrete using low-
quality recycled aggregate, type L. This type of concrete produced with
type L RCA includes backfilling, filling, and levelling concrete. In addition,
the use of type B blended cement is required as a measure against alkali-
silica reactivity.
In Hong Kong, two sets of specifications are used for the use of recycled
aggregates in concrete production. The specification requirements for RCA
are listed in Table 4.3. According to these specifications, 100% recycled
coarse aggregate may be used for low-grade applications, and recycled fines
are not allowed for use in concrete. The compressive strength for concrete
with 100% RAC is capped at 20 MPa, which can be used in benches,
planter walls, mass concrete, and other minor concrete structures. For
higher-grade applications, up to C35, the Hong Kong specifications allow a
maximum of 20% replacement of virgin aggregates by recycled aggregates.
In the United Kingdom, British Standard (BS) 8500-2 and BS EN
12620:2002-A1:2008 have included the general specifications for RCA and
RAC in their latest editions. The United Kingdom has not been as active in
concrete recycling as some of the other European countries; the older stan-
dards, BS 882 and BS 1047, only cover NAs and air-cooled blast slag aggre-
gates, respectively, and did not include any provisions for recycled aggregates.
However, these standards have already been withdrawn and replaced with BS
EN 12620:2002. The use of recycled aggregates in concrete was first allowed
according to BS 8500, published in 2002. According to BS 8500-2, the coarse
RCA and coarse recycled aggregate shall conform to the requirements speci-
fied in Table 4.4. Composites of coarse RCA or coarse recycled aggregate and
NAs shall conform to the general requirements for aggregates as specified in
BS EN 12620 and to the general requirements for normal-weight aggregates.
Although general recycled aggregates (including nonconcrete waste) can only
be used in low-grade concrete not exceeding 20 MPa characteristic strength,
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